1. Field of the Invention
This invention relates to a novel class of compounds useful in stabilizing organic materials against the effects of heat and light. The materials to be protected by these compounds include organic polymers such as polyolefins and more particularly, polyethylene and polypropylene, and the invention includes compositions containing such polymers and said stabilizers incorporated therein.
2. Description of the Prior Art
Metal salts of thio-bis-phenols have been known as rubber antioxidants for a long time (U.S. Pat. No. 2,310,449 -- 1943). In particular, nickel salts have been found to be very effective (U.S. Pat. No. 2,380,299 -- 1945). These salts have also been found useful as lubricating oil additives (U.S. Pat. No. 2,402,448 -- 1946). Nickel salts of para-alkylphenol sulfides have furthermore found use in polypropylene (U.S. Pat. No. 2,971,940 -- 1961), polyethylene (U.S. Pat. No. 2,971,941 -- 1961) as well as in other polyolefins (U.S. Pat. No. 3,006,886 -- 1961). Because of the ease of its preparation (U.S. Pat. No. 2,971,968 -- 1961; U.S. Pat. No. 3,390,160 -- 1968) -- the para-tetramethylbutylphenol sulfide nickel salt has become the article of commerce. One of its advantages is that it is compatible with other additives that are commonly used in stabilizing polyolefins such as phenolics, thiodipropionates, phosphites, benzophenones and benzotriazoles (U.S. Pat. No. 3,006,885; 3,006,886; 3,074,910; 3,167,526; 3,481,897; 3,637,588). pg,4
Recently the butylamine complex of the nickel 2,2'-thio-bis(4-tetramethylbutylphenolate) has made great inroads on the market of the above named predecessor, mainly because of its increased activity (U.S. Pat. No. 3,215,717 -- 1965). This compound too is compatible with the usual compounding ingredients used in polyolefins (U.S. Pat. No 3,218,294; 3,379,680; 3,481,897).
Most recently the alkanolamine complexes of nickel 2,2'-thio-bis(4-alkylphenolates) have been patented (U.S. Pat. No. 3,636,023 -- 1972).